Gas-enhanced electrosurgery involves the delivery of electrical current in an ionized gas stream directed onto tissue to achieve an electrosurgical effect. Gas-enhanced electrosurgery was originally conceived to improve electrosurgical coagulation, or hemostasis, to stop blood from flowing from incised tissue. The principal US patent which describes gas-enhanced electrosurgical coagulation is U.S. Pat. No. 4,781,175. This patent describes a coagulation handpiece having a nozzle with an interior passageway through which the gas is directed in a flow stream or jet to the tissue. An electrode is recessed entirely within the nozzle to ionize the gas and to conduct the electrical energy in the flow stream to the tissue. The gas stream from the nozzle clears accumulated blood on the surface of the tissue and allows the electrical energy to interact directly with the tissue and create an eschar or seal on the surface of the tissue which prevents further bleeding from the tissue. The recessed position of the electrode within the nozzle avoids contacting the electrode with the tissue or the eschar in such a way to open the tissue to bleeding. The ionization and conductivity characteristics of the gas stream also enhances the energy distribution on the tissue to obtain superior hemostatic effects.
Other secondary benefits of gas-enhanced electrosurgical coagulation have been recognized. The gas, which is typically argon that is both chemically and physiologically inert, displaces the air which contains oxygen from the surgical site. The absence of oxygen at the surgical site minimizes any burning or charring effect of the electrical energy on the tissue. The absence or reduction of burned or charred tissue facilitates and increases normal physiological healing. The absence of oxygen also eliminates or substantially reduces smoke and pungent odors which are typical during conventional electrosurgery.
The minimization or elimination of burning, charring, smoke and odor have been recognized as desirable during electrosurgical cutting as well as during electrosurgical coagulation. Gas delivery to the tissue was then used during electrosurgical cutting. An instrument or handpiece that delivered gas during both coagulation and cutting is described in U.S. Pat. No. 5,088,997. The handpiece described in this patent uses a nose piece which concentrically surrounds a single electrosurgical electrode. The gas is delivered to the nose piece where it is distributed around the electrosurgical electrode. To achieve coagulation, the nose piece is moved longitudinally forward so that only a small amount of the distal tip of the electrode is exposed. To achieve cutting, the nose piece is moved longitudinally rearward to expose more of the distal tip of the electrosurgical electrode. Gas is delivered in both positions of the nose piece, and the distal tip of the electrode is exposed in both positions. Exposing more of the distal tip of the electrode is required when cutting tissue.
U.S. Pat. No. 5,098,430 describes a variation on a gas-enhanced cutting and coagulation handpiece. In this circumstance, a nozzle completely surrounds the electrode. For coagulation, the nozzle is moved to a forward position in which the distal tip of the electrode is completely recessed within the nozzle, in the same desirable manner as was described in U.S. Pat. No. 4,781,175. For cutting, the entire nozzle is moved backward to expose the distal tip of the electrode.
A further approach to the use of gas-enhanced electrosurgical coagulation with conventional electrosurgical cutting is described in U.S. Pat. No. 5,449,356. In this patent, a separate gas-enhanced electrosurgical coagulation device with a nozzle and a recessed active electrode is combined in a single instrument with a second active electrode that is used exclusively for electrosurgical cutting. No gas is delivered when the second active electrode is used to cut tissue. Instead, the tissue cutting proceeds in a still-air environment in the same manner as has been done for many previous decades in conventional electrosurgery. The second active electrode may be fixed in position, or the second active electrode may be made extendable and retractable to eliminate its presence from the surgical site during gas-enhanced electrosurgical coagulation. The primary benefit of this type of instrument is that the surgeon has both conventional electrosurgical cutting and gas-enhanced electrosurgical coagulation available from the same handpiece or instrument. The surgeon need only switch between the two different types of electrosurgical functionality when using the singular instrument.
Another approach to cutting tissue with the use of gas-enhanced electrosurgery is represented in U.S. Pat. No. 7,004,939 and Australian application AU 200071586, published May 16, 2002. The approach described in these documents is to entirely replace a nozzle assembly used on a multiple-use handpiece of the type described in U.S. Pat. No. 4,781,175. The typical nozzle assembly described in U.S. Pat. No. 4,781,175 includes a housing which defines the nozzle and which supports an electrosurgical electrode at a position recessed within the nozzle. U.S. Pat. No. 7,004,939 and the Australian application simply replace the nozzle assembly with the recessed electrode with a different nozzle assembly in which the distal tip of the electrode protrudes for cutting. This approach requires that a multiple-use, reusable handpiece be employed. One of the features of a multiple-use handpiece is that the nozzle assembly can be removed and replaced, as is necessary for sterilization and after many uses of the nozzle assembly. However, many surgeons and medical facilities prefer to use single-use electrosurgical handpieces. Single-use handpieces are supplied in a sterilized form in a sterile package, thereby eliminating the cost and risk associated with sterilizing multiple-use instruments prior to the procedure. After the procedure is completed, the single-use handpiece is simply disposed of. The cost of a multiple-use handpiece is so much greater than the cost of a disposable single-use handpiece that it may be more economical to use the disposable handpieces when the costs of labor for sterilizing the multiple-use handpiece and its components are considered.